Potentiometer or adjustable electric resistance



R. D. BUGEL 2,479,206

POTENTIOMETER OR ADJUSTABLE ELECTRIC RESISTANCE Aug. 16, 1949.

Filed April 23, 1946 INVENTOR. 05; 0F fi/R/f BUGEL 2 v z/ ATTORNEY Patented Aug. 16, 1949 POTENTIOMETEB R ADJUSTABLE [LIC- TBIC RESISTANCE Boelof Dirk Biigel, Elndhoven,

Ilsn llnments, to Hartford Netherlands, as-

Application April 23,1940, sci-u No. 004,118

- In the Netherlands August 1, 1942 Section 1, Public Law 69, bllllfitui, 1.

Patent expires A e-st 2 Claims. (01. 201-48) 1 This invention relates to potentiometers or adjustable electric resistances (hereinafter briefly referred to as "potentiometers) constituted by a ring which is covered with resistance material and provided with an arm radially extending to the interior and carrying a shaft which is coaxially arranged in the ring and has a sliding contact secured to it.

In the known constructions either the arm constitutes one piece with the ring or the arm extending to the interior is secured to the ring by means of screws, the ring exhibiting a recess for centring or holding the arm in position. The manufacture of such recesses is generally laborious, more particularly if insulating material is concerned, such as ceramic material. In this case an accurate engagement must be ensured by polishing and this polishing of a recess requires accurately profiled grinding wheels which rapidly wear away. The manufacture of the shaft carrier in one piece with the ring entails the drawback that a high accuracy is required and for every size of potentiometer all parts must be made with different dimensions, while the fixed arm causes trouble in winding.

The present invention provides a form of construction which obviates this drawback and in which an exactly fitting surface may be provided for example, by polishing, in a simple manner. l

According to the invention, the ring comprises an arm constituted by two parts, one of which forms a projecting part which is directed toward the interior of the ring and the other a bearing for the shaft. The projecting parts may be ground off in a simple manner. Preferably, the bounding surface "between the projecting part and the bearing is given the shape of a cylindrical surface whose axis is normal to the surface of the ring. The radial dimensions of the projecting part may be small. It is sufllcient when they are such as to enable a ground surface to be provided without the grinding being rendered difficult by the ring.

The construction according to the invention permits the utilization of the same bearing with resistances having rings of different diameters. A method which is preferably utilised for the manufacture of these potentiometers with different diameters of the rings consists in that the projecting parts of the rings are so varied in en gth that one bearing fits any ring, 1. e. that with any ring the bearing gives a position coaxial if the shaft.

The use of this method permits a considerable saving in the number of bearings which have to 2 be made of diiferent dimensions and in the number of bearings which have to be kept in store.

The invention will be more clearly understood by reference to the accompanying drawing showing, by way of example, a few embodiments it the bearing I and a screw I. The projecting part and the bearing jointly constitute an arm which coaxially carries the shaft 1 in the ring. On one side the shaft bears on the bearing by means of a nipple I and on the other side on a contact member I! through the intermediary of an insulating part 8. Said contact member is secured, for example by means of a hollow rivet, to the ring I and embraces the neck of the part I. The latter carries, in addition, the arm III which carries at its end in a cavity a brush II which is constituted by carbon and metal powder and is connected, by means of a wire II, to a ring I! located between the arm I 9 and the member If. This ring and the arm III are locked against rotation relatively to the insulating part 8 and the latter in turn relatively to the shaft 1. A. layer of enamel indicated by II is frequently applied to protect the resistance wire.

The projecting part 4 is cylindrically ground out at the interior and the bearing is externally turned to form a cylinder having a corresponding diameter. An exact engagement is thus obtained in a simple manner which has, in addition, the advantage that a rotation of the bearing about the shaft of the screw I is not possible. The locking against such a rotation is intensified, according as the radius of the cylindrical surface is smaller. It is consequently advantageous to give the projecting part 4 as large a size as is possible with a view to the winding and the construction of the bearing 8. Consequently, a single screw generally suffices to fasten the bearing. In large potentiometers only use is made of more screws.

It is evident that also a plane bounding surface may be polished on the projecting part 4. In this case also the advantage is obtained that pronled grinding discs are not required. The grinding device is then less simple, however. and the fastening ofthe bearing less rigid than with a cylindrical bounding surface.

Fig. 3 shows diagrammatically aseries of three potentiometers. It can be clearly seen from the figure, how the same bearing may be nsedcfor three different rings by varying the .proiectin: part 4.

What I claimjs:

1. A potentiometer comprising a ring member of insulating material, a resistance element supported by said ring member, a shaft member concentric with said ring member, a radially inwardly extending arm member comprising 'an inwardly projecting portion of said ring member and a bearing member for said shaft member, said bearing member and said projecting portion having a contact bounding surface which is a cylindrical surface the axis of which is normal to the surface of said ring member, said arm member supporting said shaft member from said ring member, and a sliding contact member rotatably secured to said shaft member and arranged to slideably contact said resistance element.

2. A potentiometer comprising a ring member of insulating material, a resistance element supported by said ring member, a shaft member conthe length ofcentric with said ring member, a radially inwardly extending arm member comprising an inwardly projecting portion of said ring member and a bearing member for said shaft member, said bearing member and said projecting portion having a contact bounding surface which is a cylindrical surface the axis of which is normal to the surface of said ring member, means to secure said bearing member to said projectingportion whereby said arm member supports said shaft member from said ring member, and a sliding contact member rotatably secured to said shaft member and arranged to slideably contact said resistance element.

ROEIDF max-silent REFERENCES crrnn The following references are of record in the file of this patent:

Number Name Date 1,776,684 Rhodus Sept. 23, 1930 1,917,875 Weichelt July 11, 1933 2,069,440 Hethom Feb. 2, 1937 

